Heat exchanger

ABSTRACT

A heat exchanger comprising: a plurality of tubes inside of which a fluid passes; fins which are joined to the outer surfaces of the tubes and promote heat exchange between a fluid passing around the tubes and the fluid passing through inside the tube; and tank sections comprising core plates having insertion holes formed for the tubes to be inserted therein and tank bodies having the core plates joined thereto for distributing or collecting the fluid to be passed through the tubes; the tube comprises a first and a second tube plates joined in opposition to each other and inner fins disposed between the first and second tube plates, and that the portion of the tube to be inserted into the insertion hole of the core plate has generally the same outer shape as the periphery of the insertion hole, and that the portions of the first and second tube plates not to be inserted into the insertion hole of the core plate have overlapping sections which overlap each other in laminating direction of the tubes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger and, more particularly, to a heat exchanger for a supercharger in an internal combustion engine.

2. Description of Related Art

Conventionally, a heat exchanger for a supercharger in an internal combustion engine used for cooling thermally-expanded intake air in order to increase charging efficiency of the intake air has been known, for example from Japanese Patent Publication No. 2002-286394, which discloses a heat exchanger having a pair of tanks, a plurality of tubes through which super-charged air passes, and fins for increasing heat discharge, brazed together in one unit. In such a heat exchanger, the tank comprises a tank body and a core plate, and the tubes are inserted through insertion holes formed in the core plate.

In such a heat exchanger, in order to further increase heat exchange efficiency, inner fins are provided inside the tubes. In mounting the inner fins inside the tubes, in one method, the inner fins are slid and inserted into the tubes, so that mutual contact may peel off brazing material and cause a defect in a brazed portion, leading to leakage of cooling water. Therefore, in a known structure, as shown in FIG. 14, a tube 201 is formed by fitting one tube plate 201 a having inner fins 201 c placed thereon onto the other tube plate 201 b, and this tube 201 is inserted through a tube insertion hole 202 of the core plate.

In such a structure, however, as shown in FIG. 15, the tube plates 201 a, 201 b fitted together may be opened in the bent portion, called “tati” in Japanese, bent in the U-shaped cross section, which has squared corners at the bottom side thereof, due to a draft angle at the time of press shaping or spring-back of the material. As a result, there is a problem that a gap may be formed at the fitting section 201 f and may cause a brazing failure in the brazed portion.

Also, there is a problem that, as shown in FIG. 16, a step 201 g is produced as a result of forming the fitting section 201 f, and this step increases the clearance between the tube 201 and the opening edge of the tube insertion hole 202 through which the tube 201 is inserted, leading to brazing failure.

Further, when a heat exchanger of larger size is used, it is very difficult to achieve sufficient positioning accuracy of individual components, and therefore, it is required to use a jig or the like for adjustment, leading to another problem of increasing the number of processing steps.

SUMMARY OF THE INVENTION

In view of above problems, it is an object of the present invention to provide a heat exchanger that is capable of being manufactured in small number of processing steps and exhibiting a good brazing performance.

In order to accomplish the above object, according to a first aspect of the present invention, there is provided a heat exchanger comprising: a plurality of tubes (104) inside of which a fluid passes; fins (105) which are joined to the outer surfaces of the tubes (104) and promote heat exchange between a fluid passing around the tubes (104) and the fluid passing through inside the tube (104); and tank sections (101, 102) comprising core plates (101 b, 102 b) having insertion holes (101 c, 102 c) formed for the tubes (104 ) to be inserted therein and tank bodies (101 a, 102 a) having the core plates joined thereto for distributing or collecting the fluid to be passed through the tubes; the tube (104) comprises a first and a second tube plates (104 a, 104 b) joined in opposition to each other and inner fins (109) disposed between the first and second tube plates (104 a, 104 b), and that the portion of the tube (104) to be inserted into the insertion hole of the core plate has generally the same outer shape as the periphery of the insertion hole, and that the portions of the first and second tube plates (104 a, 104 b) not to be inserted into the insertion hole of the core plate have overlapping sections (104 a, 104 b) which overlap each other in laminating direction of the tubes.

In accordance with the first aspect, the portion of a tube to be inserted into an insertion hole of the core plate may be formed to have generally the same shape as the periphery of the insertion hole so that brazing performance of the core plate and the tube can be improved. Also, in accordance with the first aspect, the portions of the first and the second tube plates to be inserted into the insertion hole of the core plate have overlapping sections that overlap each other in the tube laminating direction. Therefore, by using a jig or the like to compress the overlapping sections in the tube laminating direction, the overlapping sections can be securely abutted to each other and brazing performance can be thereby improved.

In accordance with the second aspect, the overlapping sections (104 c, 104 d) are formed by attaching inner surfaces of the first tube plate (104 a) and the second tube plate (104 b) to each other. Therefore, in accordance with the second aspect, the tube plates can be formed in a shape that permits easy molding.

In accordance with the third aspect, the overlapping sections (104 c, 104 d) are fixed in calking by bending one of the first tube plate (104 a) and the second tube plate (104 b). By fixing the overlapping sections in the shape of joined hands in calking, the overlapping sections can be more securely fixed and brazing performance can be further improved.

In accordance with the fourth aspect, said overlapping sections are formed outside of said tube, with the end section of the tube in the longitudinal direction of said overlapping section abutted to said core plate. In accordance with the fourth aspect, as the end section of the tube in the longitudinal direction of the overlapping section is abutted to the core plate, positioning in the longitudinal direction of the tube relative to the core plate can be accomplished without requiring any jig.

Incidentally, the reference numerals in parentheses, to denote the above means, are intended to show the relationship of the specific means which will be described later in an embodiment of the invention.

The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a heat exchanger 100 according to the present invention;

FIG. 2 is a sectional view showing a tube 104 according to a first embodiment of the present invention;

FIG. 3 is a perspective view showing the tube 104 according to the first embodiment of the present invention;

FIG. 4 is a sectional view showing the tube 104 according to the first embodiment of the present invention as fitted to the core plate 101 b;

FIG. 5 is a perspective view showing the tube 104 according to the first embodiment of the present invention as fitted to the core plate 101 b;

FIG. 6 is an enlarged sectional view showing the tube 104 according to the first embodiment of the present invention as fitted to the core plate 101 b;

FIG. 7 is a sectional view showing a variant of the tube 104 according to the first embodiment of the present invention;

FIG. 8 is a sectional view showing a variant of the tube 104 according to the first embodiment of the present invention;

FIG. 9 is a sectional view showing a variant of the tube 104 according to the first embodiment of the present invention;

FIG. 10 is a sectional view showing a tube 104 according to a second embodiment of the present invention;

FIG. 11 is a sectional view showing a variant of the tube 104 according to the second embodiment of the present invention;

FIG. 12 is a sectional view showing a variant of the tube 104 according to the present invention;

FIG. 13 is a partial sectional view showing a variant of the tube 104 according to the present invention;

FIG. 14 is a sectional view showing a tube 201 according to a prior art;

FIG. 15 is a sectional view showing a tube 201 according to a prior art in opened state; and

FIG. 16 is a sectional view showing a tube 201 according to a prior art as fitted to a tube insertion hole 203 a of the core plate 203.

DESCRIPTION OF PREFERRED EMBODIMENTS

Now, the present invention will be described in detail with reference to appended drawings showing embodiments thereof. A heat exchanger according to the present invention is suitable to be applied to an apparatus for cooling intake air used in a supercharger of an internal combustion engine. FIG. 1 is a front view showing a heat exchanger 100 according to the present invention. The heat exchanger 100 comprises a pair of tanks 101, 102 and a heat exchanging core section 103 for heat exchange between the supercharged air and external air, brazed in one unit.

The tanks 101, 102 are composed of tank bodies 101 a, 102 a and core plates 101 b, 102 b, respectively. The core plates 101 b, 102 b have tube insertion holes 101 c, 102 c formed therein for inserting tubes 104. An inlet pipe 107 is connected to the upper end portion of the tank 101 as an inlet for supercharged air. An outlet pipe 108 is connected to the upper end portion of the tank 102 as an outlet for supercharged air.

The heat exchanging core section 103 has the tanks 101, 102 connected thereto, and comprises a plurality of tubes 104, fins 105 that are joined to outer surface of these tubes 104 and thereby thermally connected to tubes 104 for promoting heat discharge of the supercharged air, and side plates 106 disposed outside in laminating direction of the tubes 104. Material of the tubes is red brass containing 15% zinc and 0.8% iron.

The tube 104 comprises a first and second tube plates 104 a, 104 b each generally in the U-shaped cross section, which has squared corners at bottom side thereof, and fitted together so as to be opposed to each other, and inner fins 109 disposed inside the tubes 104 for promoting heat exchange between the supercharged air and external air. Brazing paste (specifically, brazing paste consisting of 75% copper, 15% tin, 5% nickel and 5% phosphor) is applied to inner surfaces of the tube plates 104 a, 104 b for brazing the inner fins.

In the first and the second tube plates 104 a, 104 b, end edges bent in horizontal direction extend over the distance between the core plate 101 b and the core plate 102 b in the direction of the longitudinal axis. With such construction, when these tube plates 104 a, 104 b are fitted together, as shown in FIG. 3, overlapping sections 104 c, 104 d are formed with both inner surfaces of the tube plates 104 a, 104 b abutted to each other. When the tube 104 is fitted to the core plate 101 b and the core plate 102 b, both ends of these side edges in the direction of longitudinal axis of these side edges are abutted to the core plates 101 b, 102 b so that tube 104 can be reliably sealed.

At both ends of the tube plates 104 a, 104 b, the side edge is not bent in the horizontal direction, and the cross-section of these ends has generally the same shape as the periphery of the tube insertion holes 101 c, 102 c. With such construction, by inserting the first and the second tube plates 104 a, 104 b into the tube insertion holes 101 c, 102 c, the first and the second tube plates 104 a, 104 b can be positioned securely relative to each other.

Next, the method of manufacturing the heat exchanger of the present invention will be described. The tube is provisionally assembled with the first and the second tube plates disposed in opposition to each other such that the inner fins are sandwiched therebetween and respective overlapping sections overlap each other. The provisionally assembled tubes and fins are laminated alternately, and each end of the tube is inserted into the tube insertion hole of the core plate, and the heat exchanging core section is provisionally assembled. The provisionally assembled heat exchanging core section is compressed in the tube laminating direction by winding wire around it, and is heated in a furnace to be integrally brazed in one unit. Then, the tank bodies 101 a, 102 a having the inlet pipe 107 and the outlet pipe 108 assembled to the core plates 101 b, 102 b, is joined by welding or the like. The first tube plate 104 a and the 30 second tube plate 104 b form two overlapping sections 104 c, 104 d with surfaces overlapping each other in the portion where they are not inserted into the tube insertion holes 101 c, 102 c of the core plates 101 b, 102 b. Since surfaces of the first tube plate 104 a and the second tube plate 104 b are abutted to each other in this manner, the first tube plate 104 a and the second tube plate 104 b can be stably positioned relative to each other so that good brazing performance can be achieved. Also, as the overlapping sections are formed so as to overlap in the tube laminating direction, when the tubes are brazed while being compressed in the tube laminating direction, the overlapping sections can be securely abutted to each other and brazing performance can be thereby improved.

On the one hand, as shown in FIG. 4, the first and the second tube plates 104 a, 104 b have the outer surface of the tube 104 abutted to the periphery of the tube insertion holes 101 c, 102 c at both ends inserted into the tube insertion holes 101 c, 102 c of the core plates 101 b, 102 b. Thus, the first and the second tube plates 104 a, 104 b can be positioned by the tube insertion holes 101 c, 102 c at both ends inserted into the tube insertion holes 101 c, 102 c of the core plates 101 b, 102 b, so that a good brazing performance can be obtained.

On the other hand, the first and the second tube plates 104 a, 104 b may be abutted to the core plates 101 b, 102 b at both ends of the overlapping sections 104 c, 104 d in the direction of longitudinal axis so that the first and the second tube plates 104 a, 104 b can be securely positioned without need for adjustment using a jig relative to the core plates 101 b, 102 b, and good brazing performance can be thereby obtained. As has been described above, a heat exchanger exhibiting good brazing performance can be manufactured with a small number of processing steps.

The present embodiment adopts the construction in which two overlapping sections 104 c, 104 d are formed by attaching inner surfaces of the first tube plate 104 a and the second tube plate 104 b, so that abutting state of the overlapping sections 104 c, 104 d is further enhanced by the weight of the laminated first and the second tube plates 104 a, 104 b and brazing performance can be thereby further improved.

As for the form of overlapping sections 104 c, 104 d in the shape of joined hands, the construction as shown in FIG. 8 may be adopted in which only one of the two tube plates 104 a, 104 b has a bent edge and the other has a flat edge. This construction has the advantage that only one of the tube plates needs to be subjected to edge bending processing.

Besides the above-described shape, of joined hands, in which inner surfaces of the first and the second tube plates 104 a, 104 b are abutted to each other, the overlapping sections 104 c, 104 d can also be constructed such that, as shown in FIG. 9, the inner surface of the first tube plate 104 a is attached to the outer surface of the second tube plate 104 b. In this construction, the end edge of the first tube plate 104 a is bent so as to situated outward by an amount corresponding to the thickness of the tube plate 104 a such that it can cover the second tube plate 104 b having a U-shaped cross section, which has squared corners at bottom side thereof. Needless to say, the first tube plate 104 a and the second tube plate 104 b can be constructed conversely.

As a variant of the overlapping sections 104 c, 104 d, the two overlapping sections 104 c, 104 d may be formed by bending one end edge of the first and the second tube plates 104 a, 104 b, respectively, and by calking these tube plates 104 a, 104 b. With such construction, the overlapping sections 104 c, 104 d can be more securely fixed and the brazing performance can be further improved.

Next, a second embodiment of the present invention will be described. This embodiment differs from the above-described embodiment only in that, as shown in FIG. 10, the tube 104 is composed of one tube plate and one overlapping section 104 c is formed by attaching the inner surface of the tube plate 104 a to itself. Therefore, explanation of same constituents as in the above-described embodiment is omitted.

In this embodiment, the tube 104 comprises a tube plate 104 a that is bent and folded so as to form a passage for gas and has two longitudinal end edges, and inner fins 109 that are disposed inside the tube 104 for promoting heat exchange between the gas and fluid. In the portion of the tube 104 that is not inserted into tube insertion holes 101 c, 102 c, the tube plate 104 a forms an overlapping section 104 c with its surface attached to itself, and both ends of the overlapping section 104 c in the direction of longitudinal axis are abutted to the surfaces of the core plates 101 b, 102 b. It is preferred that, as shown in FIG. 11, the overlapping section 104 c be fixed by calking in the same manner as in the above-described embodiment.

With respect to manufacturing method, this embodiment differs from the first embodiment in that, unlike the first embodiment in which the first and the second tube plates 104 a, 104 b are fitted to each other, in the present embodiment, after the inner fins 109 are placed on the tube plate 104 a, the tube plate 104 b is bent so as to form the tube 104 in tubular shape. With such construction, same operative effect as in the previous embodiment can be obtained, that is, a heat exchanger capable of being manufactured in small number of processing steps and exhibiting good brazing performance can be provided.

Finally, variants of both ends of the tube 104 which are inserted into the tube insertion holes 101 c, 102 c of the core plates 101 b, 102 b will be described. In a first variant, as shown in FIG. 12, the first tube plate 104 a is constructed such that the end edges 104 c′, 104 d′ are fitted inside the end edges 104 c″, 104 d″ of the second tube plate 104 b. In a second variant, as shown in FIG. 13, the firsthand the second tube plates 104 a, 104 b are constructed such that the end edges 104 c′, 104 c″ are bent inward and the outer surfaces are abutted to each other. As, in these variants, the first and the second tube plates 104 a, 104 b are abutted to the whole periphery of the tube insertion holes 101 c, 102 c of the core plates 101 b, 102 b, the first and the second tube plates 104 a, 104 b can be securely positioned and brazing performance can be thereby improved.

While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. A heat exchanger comprising: a plurality of tubes inside of which a fluid passes; fins which are joined to the outer surfaces of said tubes and promote heat exchange between a-fluid passing around said tubes and the fluid passing through inside said tube; and tank sections comprising core plates having insertion holes formed for said tubes to be inserted therein and tank bodies having said core plates joined thereto for distributing or collecting the fluid to be passed through said tubes; characterized in that said tube comprises a first and a second tube plates joined in opposition to each other and inner fins disposed between said first and second tube plates, and that the portion of said tube to be inserted into said insertion hole of said core plate has generally the same outer shape as the periphery of said insertion hole, and that the portions of said first and second tube plates not to be inserted into said insertion hole of said core plate have overlapping sections which overlap each other in laminating direction of said tubes.
 2. A heat exchanger as claimed in claim 1, wherein said overlapping sections are formed by attaching inner surfaces of said first tube plate and said second tube plate to each other.
 3. A heat exchanger as claimed in claim 2, wherein said overlapping sections are fixed in calking by bending one of said first tube plate and said second tube plate.
 4. A heat exchanger as claimed in claim 1, wherein said overlapping sections are formed outside said tube, and the end portion of said overlapping section in the tube longitudinal direction is abutted to said core plate. 